Vibrating screens are used by a number of industries, e.g., mining, food processing, sand-and-gravel, etc., to separate a fine portion of a heterogeneous substance from a coarse portion. For example, the mining industry (e.g., taconite processing) uses vibrating screens after the ore is crushed to separate fine ore from coarse ore. Typical screening processes involve placing a heterogeneous substance that comprises fine and coarse portions atop a screen. The screen is then vibrated so that the fine portion passes through the screen and the coarse portion stays atop the screen.
Typically, an electric motor having a rotating unbalance vibrates the screen. Electrical unbalance motors are usually heavy and bulky and normally require considerable maintenance and a heavy support structure. Another disadvantage is that such a configuration normally involves several moving parts, many of which are heavy and bulky, and a number of bearings. These moving parts and bearings require considerable maintenance and generate heat and excessive audible noise. Moreover, a substantial portion of the energy output of the electric motor typically goes into the useless elastic deformation of the heavy support structure and the generation of audible noise and heat.
To put this into perspective, the use of the above-type of vibrating screens during taconite processing will be used by way of example. Many of the screening operations used during taconite processing involve a motor vibrating a load that is at least 17 times the load of taconite to be screened. Moreover, the noise generated by the vibrating screens used in taconite processing may result in work environment safety issues. The taconite industry has identified vibrating screens as being responsible for substantial maintenance costs and production losses.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for vibrating screens that are smaller and lighter, that have fewer moving parts and fewer bearings, and that consequently are less noisy, require less maintenance, have reduced downtimes, and are more energy efficient than conventional vibrating screens.